Graphene oxide wrapped magnetic nanoparticles composites induced by SiO₂ coating with excellent regenerability

Graphene oxide (GO) wrapped Fe₃O₄ nanoparticles were prepared by coating the Fe₃O₄ nanoparticles (NPs) with SiO₂ layer, and then modifying by amino groups, which interact with the GO nanosheets to form covalent bonding. The SiO₂ coating layer plays a key role in integrating the magnetic nanoparticles with the GO nanosheets. Effect of the amount of SiO₂ on the morphology, structure, adsorption and regenerability of the composites was studied in detail. Results suggest that an appropriate SiO₂ layer can effectively induce the GO nanosheets to completely wrap the Fe₃O₄ NPs, forming a core-shell Fe₃O₄@SiO₂@GO composites where Fe₃O₄@SiO₂ NPs were firmly encapsulated by GO nanosheets. As an adsorbent to remove Pb(II) cations from waste water, the optimized Fe₃O₄@SiO₂@GO sample exhibits a high saturated adsorption capacity of 253 mg•g^-1, and the adsorption process is well fitted by Langmuir adsorption model. Notably, it displays an excellent regeneration, maintaining ~90% adsorption capacity for 5 cycles, while other samples decrease their adsorption capacity rapidly. This work could provide a theoretical guidance to improve the regeneration of the GO based adsorbents.